BIOLOGY AND HUMAN WELFARE 7 



have seen an enemy at once. Yet ten to one its bite would have 

 been less serious to him than an attack of hookworms. So, 

 too, some of the mosquitoes in the shaded spot where first 

 he fished were more dangerous than the copper-head, for 

 within them were malarial organisms. Had these bitten him 

 he might have had a most distressing and protracted illness. 



The numerous flies which came into the house when Willie 

 left the screen door open were mostly bred as maggots in the 

 stable, and in a dead rat in the field. The common house-flics 

 are well known now to be the carriers and distributors of 

 various diseases, especially of typhoid fever. See them on those 

 blueberry pies; who can tell what germs their little feet are 

 leaving as they walk across the crust? 



A fly bites Willie's father on the ankle and folding a newspaper, 

 he proceeds to smash the flies upon the kitchen table. He does 

 not realize that it was not one of these that bit him, but a 

 very different sort of the same size and color but with a 

 strong beak, a so-called stable-fly. He kills a small fly on 

 the window pane. Though small now it would soon grow into 

 a big one, in his opinion. He is wrong again; after flies trans- 

 form from maggots into flies they grow no more. The little 

 fly was probably of quite a different sort of which the maggots 

 sometimes live in man producing great discomfort. But, again, 

 it may have been one of those little flies that live when young 

 as maggots in our rugs and carpets feeding on the clothes 

 moths. 



His wrath against the flies abated by the slaughter of some 

 dozens of them, he picks up a small package of meat delivered 

 by the butcher's boy some time ago. With a startled buzzing 

 several flies escape and make for the window. The meat 

 shows several clusters of light yellow eggs and some small 

 maggots wandering about. These are the eggs and young of 

 flies from some dead creature. One of the flies was caught 

 and crushed between the paper and the meat as he picked the 

 package up, a bluish one with three black lines between the 

 wings. It came from a sore on one of the neighbor's cows 



